The Nuclear Bomb: How It Was Made, and Which Countries Hold It Today

Key takeaways

• The bomb grew out of curiosity, not a plan for war: radioactivity (1896), Rutherford's nearly empty atom (1911), Einstein's E=mc² (1905), the neutron (1932) and fission, explained by Lise Meitner and Otto Frisch at Christmas 1938, all came from scientists who wanted to know what the world is made of.
• Tiny mass hides huge energy: turning about one gram of mass fully into energy equals roughly 20,000 tons of explosive, and in the Hiroshima bomb less than one gram of mass actually became energy.
• Fear of Hitler started the race: Einstein's letter of 2 August 1939 led to the Manhattan Project, about 130,000 workers and roughly 2 billion dollars, with secret cities at Oak Ridge, Hanford and Los Alamos where most workers did not know what they were building.
• Historians estimate about 70,000–80,000 people died instantly in Hiroshima and about 40,000 in Nagasaki, with many more by the end of 1945; whether the bombs or the Soviet entry into the war made Japan surrender is still debated.
• The US monopoly lasted only four years. Today nine countries hold about 12,200 warheads (SIPRI, January 2025): Russia about 5,459 and the US about 5,177 hold nearly nine in ten, then China about 600, France 290, Britain 225, India 180, Pakistan 170, Israel 90 and North Korea about 50.